Air maintenance tire

ABSTRACT

A self-inflating tire assembly includes an air tube mounted within a tire sidewall groove. The air tube is in contacting engagement with opposite angled groove surfaces surrounding the air tube. A segment of the air tube is flattened from an expanded diameter to a flat diameter by bending and compression of the groove in a rolling tire footprint to force air evacuated from the flattened segment along a tube air passageway. The sidewall groove extends into an annular, axially extending, sidewall surface such as an axially oriented surface of a tire chafer protrusion located in non-contacting relationship with the rim. The air tube is extruded from a rubber composition, the rubber composition comprising: a diene based rubber; from 0.25 to 5 parts by weight, per 100 parts by weight of rubber (phr), of a self-lubrication agent capable of migrating from the rubber composition to the groove surface and disposing on the groove surface as a liquid; and from 1 to 15 parts by weight, per 100 parts by weight of rubber (phr), of a vulcanization modifier for use in the second rubber composition include α,ω-bis(N,N′-dihydrocarbylthiocarbamamoyldithio)alkanes, bismaleimides, and biscitraconimides.

This invention was made with Government support under contract numberDEEE0005447 awarded by DOE. The Government has certain rights in theinvention.

FIELD OF THE INVENTION

The invention relates generally to air maintenance tires and, morespecifically, to a tire assembly incorporating an air pumping mechanisminto a tire for maintaining tire air pressure.

BACKGROUND OF THE INVENTION

Normal air diffusion reduces tire pressure over time. The natural stateof tires is under inflated. Accordingly, drivers must repeatedly act tomaintain tire pressures or they will see reduced fuel economy, tire lifeand reduced vehicle braking and handling performance. Tire PressureMonitoring Systems have been proposed to warn drivers when tire pressureis significantly low. Such systems, however, remain dependent upon thedriver taking remedial action when warned to re-inflate a tire torecommended pressure. It is a desirable, therefore, to incorporate anair maintenance feature within a tire that will self-maintain the tireair pressure in order to compensate for any reduction in tire pressureover time without a need for driver intervention.

U.S. Pat. No. 8,042,586 discloses a self-inflating tire assembly thatincludes an air tube mounted within a tire sidewall groove. The air tubeis in contacting engagement with opposite angled groove surfacessurrounding the air tube. A segment of the air tube is flattened from anexpanded diameter to a flat diameter by bending and compression of thegroove in a rolling tire footprint to force air evacuated from theflattened segment along a tube air passageway. The sidewall grooveextends into an annular, axially extending, sidewall surface such as anaxially oriented surface of a tire chafer protrusion located innon-contacting relationship with the rim.

SUMMARY OF THE INVENTION

There is disclosed a self-inflating tire assembly includes an air tubemounted within a tire sidewall groove. The air tube is in contactingengagement with opposite angled groove surfaces surrounding the airtube. A segment of the air tube is flattened from an expanded diameterto a flat diameter by bending and compression of the groove in a rollingtire footprint to force air evacuated from the flattened segment along atube air passageway. The sidewall groove extends into an annular,axially extending, sidewall surface such as an axially oriented surfaceof a tire chafer protrusion located in non-contacting relationship withthe rim. The air tube is extruded from a rubber composition, the rubbercomposition comprising: a diene based rubber; from 0.25 to 5 parts byweight, per 100 parts by weight of rubber (phr), of a self-lubricationagent capable of migrating from the rubber composition to the groovesurface and disposing on the groove surface as a liquid; and from 1 to15 parts by weight, per 100 parts by weight of rubber (phr), of avulcanization modifier for use in the second rubber composition includeα,ω-bis(N,N′-dihydrocarbylthiocarbamamoyldithio)alkanes, bismaleimides,and biscitraconimides.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by way of example and with reference tothe accompanying drawings in which:

FIG. 1 is a section view of the air tube, tire, and rim assembly withthe air tube located within a configured sidewall groove pursuant to theinvention.

FIG. 2 is an enlarged section view of the air tube within the configuredgroove of FIG. 1 with the tube in an un-flat condition.

FIG. 3 is an enlarged section view of the air tube within the configuredgroove of FIG. 1 with the tube in a flat condition.

FIG. 4 is a schematic representation of a bending region of a tiresidewall adjacent a rolling tire footprint.

FIG. 5 is a schematic representation of a tire transforming from anoriginal configuration into a bending configuration adjacent a rollingtire footprint, whereby forming multiple bending regions.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a self-inflating tire assemblyincludes an air tube mounted within a tire sidewall groove. The air tubeis in contacting engagement with opposite angled groove surfacessurrounding the air tube. A segment of the air tube is flattened from anexpanded diameter to a flat diameter by bending and compression of thegroove in a rolling tire footprint to force air evacuated from theflattened segment along a tube air passageway. The sidewall grooveextends into an annular, axially extending, sidewall surface such as anaxially oriented surface of a tire chafer protrusion located innon-contacting relationship with the rim. The air tube is extruded froma rubber composition, the rubber composition comprising: a diene basedrubber; from 0.25 to 5 parts by weight, per 100 parts by weight ofrubber (phr), of a self-lubrication agent capable of migrating from therubber composition to the groove surface and disposing on the groovesurface as a liquid; and from 1 to 15 parts by weight, per 100 parts byweight of rubber (phr), of a vulcanization modifier for use in thesecond rubber composition includeα,ω-bis(N,N′-dihydrocarbylthiocarbamamoyldithio)alkanes, bismaleimides,and biscitraconimides.

Referring to FIG. 1, a cut away section of a tire assembly 10 is shown.Tire assembly 10 includes a tire 12, a peristaltic pump assembly 14, anda tire rim 16. The tire mounts in conventional fashion to the rim 16.The tire is of conventional construction, having a pair of sidewall 30extending from bead area 40 with bead 34 to a crown or tire tread region(not shown). The tire and rim enclose a tire cavity 28.

As seen from FIGS. 2 and 3, the peristaltic pump assembly 14 includes anannular air tube 42 that encloses an annular passageway 43. The tube 42is formed of a resilient, flexible material such as plastic or rubbercompounds that are capable of withstanding repeated deformation cycles.So constructed, the tube may deform within a tire into a flattenedcondition subject to external force and, upon removal of such force,return to an original sectional configuration. In the embodiment shown,the cross-section of the tube in an unstressed state is generallycircular but other alternative tube geometries may be employed ifdesired. The tube is of a diameter sufficient to operatively pass arequisite volume of air sufficient for the purpose of pumping air intothe tire cavity to maintain the tire 12 at a preferred inflationpressure.

The tube 42 mounts closely within a groove 126 in the tire andsequentially flattens as the tire rotates. The segment by segmentflattening of the tube as the tire rotates operates to pump air alongthe air passageway 43; air which is then directed into the tire cavity28 to maintain air pressure. A peristaltic pumping system employing atube within a sidewall groove is shown in issued U.S. Pat. No.8,042,586, incorporated herein by reference in its entirety.

FIG. 1 shows a preferred location for the air tube assembly 14. The tube42 is located within a groove 126 in the sidewall 30 of the tire 12. Thetube 42 as will be explained is closed by compression strain bending thesidewall groove 126 within a rolling tire footprint. The location of thetube 42 in the sidewall 30 affords the user freedom of placement andavoids contact between the tube 42 and the rim flange 16 at surface 26.The higher placement of the tube 42 in the sidewall groove 126 uses thedeformation of the sidewall as it passes through the tire footprint toclose the tube and provide the pumping action rather than pinching thetube.

The configuration and operation of the groove 126 to flatten the tube 42is shown in FIGS. 2 and 3. The groove 126 is defined by parallelentryway sidewalls 128, 130 at a groove entryway opening 132 having anominal width W1. The width W1 is sufficient to closely admit the tube42 with interference but without constricting the air passageway 43extending through the tube 42. An interior generally triangular shapedgroove portion 134 is defined between convergent groove sidewalls 136,138. The sidewalls 136, 138 intersect entryway sidewalls 130, 128,respectively at an obtuse angle. The sidewalls 136, 138 convergeinwardly at an angle a of approximately ninety degrees and contact thesides of the tube 42 in the position shown by FIG. 1A. The sidewalls136, 138 then converge inwardly to an inward U-shaped groove flex region140 of a narrower width W2 defined between sidewalls 162, 164 as shownin FIG. 3. The sidewalls 162, 164 intersect respectively sidewalls136,138 at an obtuse angled junction designated by numerals 166, 168.The sidewalls 162, 166 extend to an inward radius end 142 of theU-shaped groove flex region 140. In the tube-expanded condition of FIG.1A, the contact of surfaces 136, 138 and 128, 130 against the tube 42 issufficient to hold the tube 42 within the groove 126.

The location of the pump assembly 14 within the tire sidewall isdistanced from the rim 16 as shown. A preferred location of the pumpassembly tube 42 is within a groove 126 positioned in a generallyaxially extending chafer surface 144. The chafer 120 extends from therim 16 and the location of the groove 126 within the surface 144 allowsa separation of the tube 42 from the rim flange 24 while efficientlytransferring tube closing forces from sidewall deformation to the tube42. As will be apparent from a combined consideration of FIGS. 2 and 3,the tube 42 positioned within groove 126 is closed or flattened bycompression due to tire sidewall 30 bending in the tire footprint 100.The force from the footprint imposes an axial directed force F2 into thesidewall 30 which acts to close the groove 126 from the openconfiguration of FIG. 2 to the closed configuration of FIG. 3. As aresult, the entryway opening 132 of the groove 126 constricts to a widthdimension W2 and the groove sidewalls 128, 130 and 136, 138 are forcedinward. Inward pressure from the sidewalls 128, 130 and 136, 138 againstthe tube 42 causes the affected segment of the tube 42 to flatten andthereby pump air evacuated therefrom along unaffected segments of theair passageway 43. Surfaces 128, 130 and 136, 138 extend from thenarrower inward groove surfaces 162, 164 defining groove portion 134.Compression forces F2 act to close the groove 126 as surfaces 162, 164and the respective surfaces 128, 130, 136, 138 extending therefrom pivotinwardly about the radius end 142 of the groove portion 140. The angledrelationship and profile of the surfaces 128, 130 to respectivecounterparts 136, 138 and 162, 164, extending from the inward U-shapedgroove portion 134, act to close such surfaces inward evenly about thecircumference of the tube 42 within the groove 126. Accordingly, thecompression forces F2 transferred into the tube 42 by the surfaces 128,130, 136, 138 are distributed about the circumference of the tube,causing an even and symmetrical flattening of the tube 42. An even andefficient pumping of evacuated air from the affected tube segmentresults. The affected segment of the tube 42 that is flattened is onlythat segment within the tire footprint. As the tire continues to rotate,each flattened segment will resume its original configuration asrepresented in FIG. 2 as an adjacent segment within the tire footprintis flattened.

FIGS. 4 and 5 illustrate in schematic representation the placement ofthe groove and air tube within a tire. As will be appreciated, thesidewalls of a rolling tire generally bend and undergo a geometrictransformation from bending strain introduced into the sidewalls as thetire rolls against a ground surface. The bending strain within sidewallregions adjacent to a tire footprint causes the radius of curvaturewithin certain such sidewall regions of the sidewalls to bend to agreater extent. In a bending region 174 of a sidewall, the regiontransforms from the unstrained configuration shown at 176 into thebending configuration shown at 178. In the bending condition, the region174 will have a neutral axis 180 that is not under strain; a compressionside 182 of the neutral axis 180 of the region 174 that is undercompression, and an elongation side of the neutral axis 180 of theregion 174 that under elongation. For placement of the groove and airtube, a bending region of the sidewall is selected that will experiencebending strain when that region is adjacent to the tire footprint. Thecompression side 182 of the region 174 is satisfactory for placement ofthe groove and tube assembly 188 since a compression of the side 182 ofthe region 174 will cause the groove to close around the air tube. Tothe contrary, the elongation side 184 of the region 174 isunsatisfactory for such a side under elongation strain, will cause thegroove to widen rather than close, and not result in a flattening of thetube. Placement of the groove and tube assembly 188 should further beplaced within the compression side 182 of the region 178 at a locationfarthest removed from the neutral axis 180, for such a location willexperience the greatest compression strain. Location of the groove andtube 188 farthest from the neutral axis 180 of the selected bendingregion 174 will accordingly expose the groove to maximum closing due toa maximum compression force and bending imposed upon the tire regionsurrounding the groove. As a result, efficient and complete closing andcollapse of the groove will be effected, causing an equally efficientand complete flattening of the air tube within the groove.

FIG. 5 illustrates in schematic form three sidewall regions of asidewall that undergo curvature bending transformation when adjacent toa tire footprint. The original tire shape 190 is shown and configuration192 is superimposed to show tire deformation adjacent to a tirefootprint. Three bending regions 194, 196, 198 (for the purpose ofillustration) are identified that will undergo strain-induced radius ofcurvature transformation adjacent a rolling tire footprint. Otherregions are available and may be selected for groove and air tubeplacement if desired. As shown, bulging of the tire into theconfiguration 178 causes the regions 194, 196, 198 to bend to a greaterextend (i.e. at a reduced radius) than within the original configuration176. Each region 194, 196, 198 will have a neutral, unstrained axis, acompression side of the axis, and an elongation side of the axis asexplained above in reference to FIG. 4. A groove and tube assembly 200,202, or 204 will be positioned to the compression side 182 of the regionselected, so that the compression of the compression side 182 will actto bend and constrict a segment of the groove adjacent to the tirefootprint. Bending and constriction of the groove segment adjacent thetire footprint will commensurately cause a bending and flattening of anair tube segment within the bending groove segment, whereby pumpingevacuated air from the flattened air tube segment along the air tubepassageway. Positioning the groove and air tube within a bending regionof the sidewall thus operates to utilize the bending compression strainwithin the region to effect a bending and collapse of the groove segmentwithin the bending region.

Utilizing the bending strain within a bending region of a sidewallavoids the need to compress the air tube by pinching the air tubeagainst a relatively hard barrier such as the tire assembly rim.Potential damage to the air tube from contact with the rim is thusavoided and the structural integrity of the air tube is preservedthroughout the life cycle of the tire.

During operation, the tube may experience cracking due to excess stressand strain due to the repetitive bending. Further, the internal surfacesof the tube may rub during flexure causing abrasion and blockage of thetube. Such cracking and internal abrasion may lead to reduce pumpingefficiency for the peristaltic tube. To reduce the likelihood ofcracking and abrasion in the tube, the tube is extruded from a rubbercomposition as further described.

Again referring to FIGS. 1, 2 and 3, the tube 43 is extruded from arubber composition.

The rubber composition includes a self-lubrication agent capable ofmigrating from the rubber composition to the groove surface anddisposing on the groove surface as a liquid. By self-lubricating, it ismeant that the self-lubrication agent will migrate by diffusion orotherwise from the bulk of the rubber composition to the groove surface,whereon the agent exists in liquid form to act as a lubricant to reducethe likelihood of cracking in the groove surface. Self-lubricatingagents that may solidify at the surface are not usable, as the formationof the solid may cause blockage of the air passageway.

Suitable self-lubrication agents include liquids having a melting pointsof less than 0° C. In one embodiment, the self-lubrication agents has amelting points of less than −10° C. Melting point may be determined bymethods as are known in the art, including ASTM D5440-93.

The self-lubrication agent may include an oil. Suitable oils include,paraffinic, and vegetable oils. Suitable vegetable oils include canola(rapeseed) oil, sunflower oil, soybean oil, castor oil, and the like.

In one embodiment, the rubber composition includes from 0.25 to 5 phr ofthe self-lubrication agent. In another embodiment, the rubbercomposition includes from 0.5 to 1.5 phr of the self-lubrication agent.

The rubber composition includes a vulcanization modifier.

In one embodiment, the vulcanization modifier for use in the secondrubber composition includeα,ω-bis(N,N′-dihydrocarbylthiocarbamamoyldithio)alkanes, bismaleimides,and biscitraconimides.

In one embodiment, the vulcanization modifier is aα,ω-bis(N,N′-dihydrocarbylthiocarbamamoyldithio)alkanes. Suitableα,ω-bis(N,N′-dihydrocarbylthiocarbamamoyldithio)alkanes include1,2-bis(N,N′-dibenzylthiocarbamoyldithio)ethane;1,3-bis(N,N′-dibenzylthiocarbamoyldithio)propane;1,4-bis(N,N′-dibenzylthiocarbamoyldithio)butane;1,5-bis(N,N′-dibenzylthiocarbamoyl-dithio)pentane;1,6-bis(N,N′-dibenzylthiocarbamoyldithio)hexane;1,7-bis(N,N′-dibenzylthiocarbamoyldithio)heptane;1,8-bis(N,N′-dibenzylthiocarbamoyl-dithio)octane;1,9-bis(N,N′-dibenzylthiocarbamoyldithio)nonane; and1,10-bis(N,N′-dibenzylthiocarbamoyldithio)decane. In one embodiment, thevulcanization modifier is1,6-bis(N,N′-dibenzylthiocarbamoyldithio)hexane available as Vulcuren®from Bayer.

In one embodiment, the vulcanization modifier is a bismaleimide.Suitable bismaleimides include N,N′-m-phenylene bismaleimide, availableas HVA-2 from DuPont.

In one embodiment, the vulcanization modifier is a citraconimide.Suitable citraconimidies include N,N′-m-xylylene biscitraconimide, alsoknown as 1,3-bis(citraconimidomethyl)benzene, available as Perkalink®900 from Flexsys.

In one embodiment, the rubber composition in one or more annularsegments may comprise from about 1 to about 15 parts by weight, per 100parts by weight of elastomer (phr), of the vulcanization modifier. Inanother embodiment, the rubber composition may comprise from about 2 toabout 8 phr of vulcanization modifier.

The rubber composition includes one or more rubbers or elastomerscontaining olefinic unsaturation. The phrases “rubber or elastomercontaining olefinic unsaturation” or “diene based elastomer” areintended to include both natural rubber and its various raw and reclaimforms as well as various synthetic rubbers. In the description of thisinvention, the terms “rubber” and “elastomer” may be usedinterchangeably, unless otherwise prescribed. The terms “rubbercomposition,” “compounded rubber” and “rubber compound” are usedinterchangeably to refer to rubber which has been blended or mixed withvarious ingredients and materials and such terms are well known to thosehaving skill in the rubber mixing or rubber compounding art.Representative synthetic polymers are the homopolymerization products ofbutadiene and its homologues and derivatives, for example,methylbutadiene, dimethylbutadiene and pentadiene as well as copolymerssuch as those formed from butadiene or its homologues or derivativeswith other unsaturated monomers. Among the latter are acetylenes, forexample, vinyl acetylene; olefins, for example, isobutylene, whichcopolymerizes with isoprene to form butyl rubber; vinyl compounds, forexample, acrylic acid, acrylonitrile (which polymerize with butadiene toform NBR), methacrylic acid and styrene, the latter compoundpolymerizing with butadiene to form SBR, as well as vinyl esters andvarious unsaturated aldehydes, ketones and ethers, e.g., acrolein,methyl isopropenyl ketone and vinylethyl ether. Specific examples ofsynthetic rubbers include neoprene (polychloroprene), polybutadiene(including cis-1,4-polybutadiene), polyisoprene (includingcis-1,4-polyisoprene), butyl rubber, halobutyl rubber such aschlorobutyl rubber or bromobutyl rubber, styrene/isoprene/butadienerubber, copolymers of 1,3-butadiene or isoprene with monomers such asstyrene, acrylonitrile and methyl methacrylate, as well asethylene/propylene terpolymers, also known as ethylene/propylene/dienemonomer (EPDM), and in particular, ethylene/propylene/dicyclopentadieneterpolymers. Additional examples of rubbers which may be used includealkoxy-silyl end functionalized solution polymerized polymers (SBR, PBR,IBR and SIBR), silicon-coupled and tin-coupled star-branched polymers.The preferred rubber or elastomers are polyisoprene (natural orsynthetic), polybutadiene and SBR.

In one aspect the at least one additional rubber is preferably of atleast two of diene based rubbers. For example, a combination of two ormore rubbers is preferred such as cis 1,4-polyisoprene rubber (naturalor synthetic, although natural is preferred), 3,4-polyisoprene rubber,styrene/isoprene/butadiene rubber, emulsion and solution polymerizationderived styrene/butadiene rubbers, cis 1,4-polybutadiene rubbers andemulsion polymerization prepared butadiene/acrylonitrile copolymers.

In one aspect of this invention, an emulsion polymerization derivedstyrene/butadiene (E-SBR) might be used having a relatively conventionalstyrene content of about 20 to about 28 percent bound styrene or, forsome applications, an E-SBR having a medium to relatively high boundstyrene content, namely, a bound styrene content of about 30 to about 45percent.

By emulsion polymerization prepared E-SBR, it is meant that styrene and1,3-butadiene are copolymerized as an aqueous emulsion. Such are wellknown to those skilled in such art. The bound styrene content can vary,for example, from about 5 to about 50 percent. In one aspect, the E-SBRmay also contain acrylonitrile to form a terpolymer rubber, as E-SBAR,in amounts, for example, of about 2 to about 30 weight percent boundacrylonitrile in the terpolymer.

Emulsion polymerization prepared styrene/butadiene/acrylonitrilecopolymer rubbers containing about 2 to about 40 weight percent boundacrylonitrile in the copolymer are also contemplated as diene basedrubbers for use in this invention.

The solution polymerization prepared SBR (S-SBR) typically has a boundstyrene content in a range of about 5 to about 50, preferably about 9 toabout 36, percent. The S-SBR can be conveniently prepared, for example,by organo lithium catalyzation in the presence of an organic hydrocarbonsolvent.

In one embodiment, cis 1,4-polybutadiene rubber (BR) may be used. SuchBR can be prepared, for example, by organic solution polymerization of1,3-butadiene. The BR may be conveniently characterized, for example, byhaving at least a 90 percent cis 1,4-content.

The cis 1,4-polyisoprene and cis 1,4-polyisoprene natural rubber arewell known to those having skill in the rubber art.

The term “phr” as used herein, and according to conventional practice,refers to “parts by weight of a respective material per 100 parts byweight of rubber, or elastomer.”

The rubber composition may also include up to 70 phr of processing oil.Processing oil may be included in the rubber composition as extendingoil typically used to extend elastomers. Processing oil may also beincluded in the rubber composition by addition of the oil directlyduring rubber compounding. The processing oil used may include bothextending oil present in the elastomers, and process oil added duringcompounding. Suitable process oils include various oils as are known inthe art, including aromatic, paraffinic, naphthenic, vegetable oils, andlow PCA oils, such as MES, TDAE, SRAE and heavy naphthenic oils.Suitable low PCA oils include those having a polycyclic aromatic contentof less than 3 percent by weight as determined by the IP346 method.Procedures for the IP346 method may be found in Standard Methods forAnalysis & Testing of Petroleum and Related Products and BritishStandard 2000 Parts, 2003, 62nd edition, published by the Institute ofPetroleum, United Kingdom.

The rubber composition may include from about 10 to about 150 phr ofsilica. In another embodiment, from 20 to 80 phr of silica may be used.

The commonly employed siliceous pigments which may be used in the rubbercompound include conventional pyrogenic and precipitated siliceouspigments (silica). In one embodiment, precipitated silica is used. Theconventional siliceous pigments employed in this invention areprecipitated silicas such as, for example, those obtained by theacidification of a soluble silicate, e.g., sodium silicate.

Such conventional silicas might be characterized, for example, by havinga BET surface area, as measured using nitrogen gas. In one embodiment,the BET surface area may be in the range of about 40 to about 600 squaremeters per gram. In another embodiment, the BET surface area may be in arange of about 80 to about 300 square meters per gram. The BET method ofmeasuring surface area is described in the Journal of the AmericanChemical Society, Volume 60, Page 304 (1930).

The conventional silica may also be characterized by having adibutylphthalate (DBP) absorption value in a range of about 100 to about400, alternatively about 150 to about 300.

The conventional silica might be expected to have an average ultimateparticle size, for example, in the range of 0.01 to 0.05 micron asdetermined by the electron microscope, although the silica particles maybe even smaller, or possibly larger, in size.

Various commercially available silicas may be used, such as, only forexample herein, and without limitation, silicas commercially availablefrom PPG Industries under the Hi-Sil trademark with designations 210,243, etc; silicas available from Rhodia, with, for example, designationsof Z1165MP and Z165GR and silicas available from Degussa AG with, forexample, designations VN2 and VN3, etc.

Commonly employed carbon blacks can be used as a conventional filler inan amount ranging from 10 to 150 phr. In another embodiment, from 20 to80 phr of carbon black may be used. Representative examples of suchcarbon blacks include N110, N121, N134, N220, N231, N234, N242, N293,N299, N315, N326, N330, N332, N339, N343, N347, N351, N358, N375, N539,N550, N582, N630, N642, N650, N683, N754, N762, N765, N774, N787, N907,N908, N990 and N991. These carbon blacks have iodine absorptions rangingfrom 9 to 145 g/kg and DBP number ranging from 34 to 150 cm³/100 g.

Other fillers may be used in the rubber composition including, but notlimited to, particulate fillers including ultra high molecular weightpolyethylene (UHMWPE), crosslinked particulate polymer gels includingbut not limited to those disclosed in U.S. Pat. Nos. 6,242,534;6,207,757; 6,133,364; 6,372,857; 5,395,891; or 6,127,488, andplasticized starch composite filler including but not limited to thatdisclosed in U.S. Pat. No. 5,672,639. Such other fillers may be used inan amount ranging from 1 to 30 phr.

In one embodiment the rubber composition may contain a conventionalsulfur containing organosilicon compound. In one embodiment, the sulfurcontaining organosilicon compounds are the 3,3′-bis(trimethoxy ortriethoxy silylpropyl) polysulfides. In one embodiment, the sulfurcontaining organosilicon compounds are 3,3′-bis(triethoxysilylpropyl)disulfide and/or 3,3′-bis(triethoxysilylpropyl) tetrasulfide.

In another embodiment, suitable sulfur containing organosiliconcompounds include compounds disclosed in U.S. Pat. No. 6,608,125. In oneembodiment, the sulfur containing organosilicon compounds includes3-(octanoylthio)-1-propyltriethoxysilane, CH₃(CH₂)₆C(═O)—S—CH₂CH₂CH₂Si(OCH₂CH₃)₃, which is available commercially as NXT™ fromMomentive Performance Materials.

In another embodiment, suitable sulfur containing organosiliconcompounds include those disclosed in U.S. Patent Publication No.2003/0130535. In one embodiment, the sulfur containing organosiliconcompound is Si-363 from Degussa.

The amount of the sulfur containing organosilicon compound in a rubbercomposition will vary depending on the level of other additives that areused. Generally speaking, the amount of the compound will range from 0.5to 20 phr. In one embodiment, the amount will range from 1 to 10 phr.

It is readily understood by those having skill in the art that therubber composition would be compounded by methods generally known in therubber compounding art, such as mixing the various sulfur-vulcanizableconstituent rubbers with various commonly used additive materials suchas, for example, sulfur donors, curing aids, such as activators andretarders and processing additives, such as oils, resins includingtackifying resins and plasticizers, fillers, pigments, fatty acid, zincoxide, waxes, antioxidants and antiozonants and peptizing agents. Asknown to those skilled in the art, depending on the intended use of thesulfur vulcanizable and sulfur-vulcanized material (rubbers), theadditives mentioned above are selected and commonly used in conventionalamounts. Representative examples of sulfur donors include elementalsulfur (free sulfur), an amine disulfide, polymeric polysulfide andsulfur olefin adducts. In one embodiment, the sulfur-vulcanizing agentis elemental sulfur. The sulfur-vulcanizing agent may be used in anamount ranging from 0.5 to 8 phr, alternatively with a range of from 1.5to 6 phr. Typical amounts of tackifier resins, if used, comprise about0.5 to about 10 phr, usually about 1 to about 5 phr. Typical amounts ofprocessing aids comprise about 1 to about 50 phr. Typical amounts ofantioxidants comprise about 1 to about 5 phr. Representativeantioxidants may be, for example, diphenyl-p-phenylenediamine andothers, such as, for example, those disclosed in The Vanderbilt RubberHandbook (1978), Pages 344 through 346. Typical amounts of antiozonantscomprise about 1 to 5 phr. Typical amounts of fatty acids, if used,which can include stearic acid comprise about 0.5 to about 3 phr.Typical amounts of zinc oxide comprise about 2 to about 5 phr. Typicalamounts of waxes comprise about 1 to about 5 phr. Often microcrystallinewaxes are used. Typical amounts of peptizers comprise about 0.1 to about1 phr. Typical peptizers may be, for example, pentachlorothiophenol anddibenzamidodiphenyl disulfide.

Accelerators are used to control the time and/or temperature requiredfor vulcanization and to improve the properties of the vulcanizate. Inone embodiment, a single accelerator system may be used, i.e., primaryaccelerator. The primary accelerator(s) may be used in total amountsranging from about 0.5 to about 4, alternatively about 0.8 to about 1.5,phr. In another embodiment, combinations of a primary and a secondaryaccelerator might be used with the secondary accelerator being used insmaller amounts, such as from about 0.05 to about 3 phr, in order toactivate and to improve the properties of the vulcanizate. Combinationsof these accelerators might be expected to produce a synergistic effecton the final properties and are somewhat better than those produced byuse of either accelerator alone. In addition, delayed actionaccelerators may be used which are not affected by normal processingtemperatures but produce a satisfactory cure at ordinary vulcanizationtemperatures. Vulcanization retarders might also be used. Suitable typesof accelerators that may be used in the present invention are amines,disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides,dithiocarbamates and xanthates. In one embodiment, the primaryaccelerator is a sulfenamide. If a second accelerator is used, thesecondary accelerator may be a guanidine, dithiocarbamate or thiuramcompound.

The mixing of the rubber composition can be accomplished by methodsknown to those having skill in the rubber mixing art. For example, theingredients are typically mixed in at least two stages, namely, at leastone non-productive stage followed by a productive mix stage. The finalcuratives including sulfur-vulcanizing agents are typically mixed in thefinal stage which is conventionally called the “productive” mix stage inwhich the mixing typically occurs at a temperature, or ultimatetemperature, lower than the mix temperature(s) than the precedingnon-productive mix stage(s). The terms “non-productive” and “productive”mix stages are well known to those having skill in the rubber mixingart. The rubber composition may be subjected to a thermomechanicalmixing step. The thermomechanical mixing step generally comprises amechanical working in a mixer or extruder for a period of time suitablein order to produce a rubber temperature between 140° C. and 190° C. Theappropriate duration of the thermomechanical working varies as afunction of the operating conditions, and the volume and nature of thecomponents. For example, the thermomechanical working may be from 1 to20 minutes.

The air tube may be extruded from the rubber composition using extrusionprocedures as are known in the art.

Vulcanization of the pneumatic tire of the present invention isgenerally carried out at conventional temperatures ranging from about100° C. to 200° C. In one embodiment, the vulcanization is conducted attemperatures ranging from about 110° C. to 180° C. Any of the usualvulcanization processes may be used such as heating in a press or mold,heating with superheated steam or hot air. Such tires can be built,shaped, molded and cured by various methods which are known and will bereadily apparent to those having skill in such art.

What is claimed is:
 1. A self-inflating tire assembly comprising: a rimhaving a tire mounting surface extending between first and second rimflanges; a tire mounted to the rim tire mounting surface, the tirehaving a tire cavity, first and second sidewalls extending respectivelyfrom first and second tire bead regions to a tire tread region; thefirst sidewall having at least one bending region operatively bendingwithin a rolling tire footprint responsive to a bending strain, wherebythe bending region in a bending condition within said rolling tirefootprint having a bending strain neutral axis, a compression side ofthe neutral zone, and an elongation side of the neutral zone; a sidewallgroove positioned within the compression side of the neutral axis of theone said bending region of the first tire sidewall; an air tubepositioned within the sidewall groove in contacting engagement withopposite groove surfaces at least partially surrounding the air tube,the sidewall groove operatively bending within the bend regionresponsive to the bending strain within the rolling tire footprint tocompress the air tube from an expanded diameter to a flat diameteradjacent the rolling tire footprint, whereby forcing evacuated air froma flattened air tube segment along the air passageway; the air tubeextruded from a rubber composition, the rubber composition comprising: adiene based rubber; from 0.25 to 5 parts by weight, per 100 parts byweight of rubber (phr), of a self-lubrication agent capable of migratingfrom the rubber composition to the groove surface and disposing on thegroove surface as a liquid; and from 1 to 15 parts by weight, per 100parts by weight of rubber (phr), of a vulcanization modifier for use inthe second rubber composition includeα,ω-bis(N,N′-dihydrocarbylthiocarbamamoyldithio)alkanes, bismaleimides,and biscitraconimides.
 2. The tire assembly of claim 1, wherein the airtube and the sidewall groove are located within a sidewall region of thefirst tire sidewall above an upper boundary of the rim.
 3. The tireassembly of claim 2, wherein the groove surfaces contact the air tubeand bend within a footprint of a rotating tire to operatively close anair tube segment within the tire footprint.
 4. The tire assembly ofclaim 3, wherein the air tube comprises an annular body extendingsubstantially a circumference of a tire first sidewall.
 5. The tireassembly of claim 4, wherein the sidewall groove is annular and locatedproximally above the upper boundary of the rim.
 6. The tire assembly ofclaim 1, wherein the groove extends into an annular, substantiallyaxially extending, sidewall surface.
 7. The tire assembly of claim 6,wherein the annular sidewall surface comprises a substantially axiallyoriented surface of a tire chafer protrusion located in non-contactingrelationship with the rim, the groove extending into the annularsidewall surface in substantially a radial direction.
 8. The tireassembly of claim 1, wherein the sidewall groove includes a sidewallgroove opening operatively sized to closely admit the air tube.
 9. Thetire assembly of claim 8, wherein substantially the entirety of the airtube resides within the sidewall groove.
 10. The tire assembly of claim9, wherein first and second angled groove surfaces define opposite sidesof the sidewall groove, each angled groove surface comprising first andsecond tube contacting surfaces adjoining at an angled intersection, andwherein the tube contacting surfaces of the first and second angledgroove surfaces operatively contact the air tube at space apartintervals surrounding and substantially circumscribing the air tube. 11.The tire assembly of claim 10, wherein the first and second angledgroove surfaces converge and join at an inward terminal groove end andoperatively flex inwardly about the terminal groove end to constrict thesidewall groove and flatten a footprint segment of the air tube withinthe groove.
 12. The tire assembly of claim 11, wherein the groovenarrows toward the terminal groove end.
 13. The tire assembly of claim12, wherein an inward portion of the groove at the terminal groove endis substantially U-shaped.
 14. The tire assembly of claim 13, whereinthe first and second angled groove surfaces converge toward the inwardportion of the groove.
 15. The tire assembly of claim 14, wherein thegroove extends into an annular, substantially axially extending,sidewall surface.
 16. The tire assembly of claim 15, wherein the annularsidewall surface comprises a substantially axially oriented surface of atire chafer protrusion located in non-contacting relationship with therim and the groove extending into the annular sidewall surface insubstantially a radial direction.
 17. The tire assembly of claim 1,wherein the sidewall groove is positioned within the compression side ofthe neutral axis of the one said bending region of the first tiresidewall at a substantially maximum distance from the neutral axis.